Lubricating and hydraulic fluids are used extensively throughout manufacturing plants and in industrial machinery. In most of these applications, the fluid is contained in a reservoir and is delivered to the desired locations by either the action of a pump or by splash-lubrication. When the fluid is pumped to the desired location, atmospheric air is drawn into the reservoir to take up the volume of the pumped out oil and thus prevent any amount of vacuum in the reservoir, as the typical reservoir is not designed for vacuum service. Additionally in equipment that may not run continuously, atmospheric air may be drawn into a reservoir due to volume changes upon cooling. This exchange of air between the reservoir and the ambient surroundings is known in the art as reservoir breathing.
For all lubricating and hydraulic systems, the need to keep the oil clean and dry is of paramount importance as equipment failure is directly linked to the presence of contaminants including particulates and water. Not only is liquid filtration commonly utilized to remove particulates from the fluid, but also measures are taken to prevent ingression of contaminants into the reservoir. One significant ingression point for contamination is through the reservoir openings that allow the reservoir to breathe. When a reservoir breathes in ambient air, contamination in the form of airborne particulates and moisture can be drawn in as well. Various methods have been used to minimize the ingression of contaminants into reservoirs.
The simplest approach used in the art is a turn down pipe 11, as shown in the reservoir 10 FIG. 1. The turn down pipe 11 basically prevents the gross ingression of liquid water when the reservoir 10 gets wet with water either from a rainstorm in exterior applications, or a washdown in interior applications. A limitation in using the turn down pipe 11 is that the turn down pipe 11 does not prevent the ingression of particulates or atmospheric moisture.
Another approach used in the art is a filter breather 13 shown in FIG. 2, where a filter media 15 is placed within a breather 14 to capture airborne particulates. Filter media 15 used in this type of filter varies widely from coarse open celled foam to fibrous filter media rated at 3-micron filtration. This approach is generally limited by pressure drop and efficiency of the filter and does nothing to prevent atmospheric moisture from entering the reservoir 12. Additionally, in order for all the air entering the reservoir 12 to get filtered, the reservoir 12 must be completely sealed except for the breathers. Otherwise as the filter element increases in pressure drop due to the accumulation of particulates, the likelihood of particulate laden air entering the reservoir through any gaps in the sealing surfaces increases significantly.
Desiccant breathers are also another type of technology used to address the issue of ingression of contaminants, as described in U.S. Pat. Nos. 4,504,289, 4,548,624, and 6,217,639 and illustrated in FIG. 3. The desiccant breather 17 of FIG. 3 is shown as comprising a desiccant material 20 to absorb moisture and a filter media 19 to remove particulate. Desiccant breathers however are limited in that they have only a finite capacity for moisture removal and thus when the desiccant is spent, do not remove any additional moisture. Users thus are required to closely monitor the conditions of the desiccant and change-out the breathers on a frequent basis.
The requirement to monitor and replace desiccant breathers adds to the overall cost of preventing ingression of contaminants into the reservoir 16. Additionally, desiccant breathers, such as desiccant breather 17, remove moisture only when the moisture is in close proximity of the desiccant material. Thus for a desiccant to remove moisture from the fluid 21 that is contained in the reservoir 16, the moisture must diffuse from the fluid surface to the desiccant material 17. As these distances are often on the order of 1 to 10 feet, the process is very slow and essentially passive.
All of the current technologies used to prevent the ingression of contaminants suffer from drawbacks resulting in less than optimal reservoir headspace condition. It is the object of the current invention to provide a means for preventing the ingression of particulate and moisture into reservoirs and to provide a means for the active removal of water and moisture from the fluid contained in the reservoir.